The Horse:Your Guide To Equine Health Care provides monthly equine health care information to horse owners, breeders, veterinarians, barn/farm managers, trainer/riding instructors, and others involved in the hands-on care of the horse.
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6 TheHorse.com THE HORSE February 2016 The New Year hasn't gotten away from you yet! Here's your step-by-step guide to cleaning up your horse-related clutter and documents: TheHorse.com/36919. WHAT'S ONLINE ■ THE HORSE HEALTH This award-winning e-newsletter offers news on diseases, veterinary research, and health events, along with in-depth articles on common equine health conditions. Supported by Zoetis . ■ HORSE WELFARE AND INDUSTRY Get the latest news on equine welfare, industry happenings, and horse-related business news. ■ SPECIALTY WEEKLY E-NEWSLETTERS Nutrition Lameness Reader Favorites MONTHLY E-NEWSLETTERS Behavior Breeding Equinomics Older Horse Care Sports Medicine Bluegrass Equine Digest is published monthly in partnership with UK Ag Equine and the Gluck Equine Research Center and is supported by Zoetis . 1 N ot all stallions are cre- ated equal and neither is the amount of sperm they produce. The most sought- after stud in the area, for in- stance, could produce minimal amounts of semen, while a less desirable horse might produce more than his breeders ever need. So what are the deciding factors when it comes to sperm production? Ed Squires, MS, PhD, Dipl. ACT (hon.), reviewed some of those factors at the 2015 World Equine Veterinary Association Congress, held Oct. 8-10 in Guadalajara, Mexico. Squires is a professor at the University of Ken- tucky's Gluck Equine Research Center, in Lexington. "It is important for both veterinar- ians and stallion managers to know the factors that affect sperm output in stallions," Squires said. Those key factors include stallion age, season, testis size, ejaculation frequency, and sex drive. Veterinarians, he said, can evaluate these factors during breeding sound- ness exams and recommend adjust- ments to help improve a stallion's sperm output. Managers, on the other hand, can use these factors to deter- mine how many mares the stallion can realistically breed in a season. Squires reviewed each factor in detail: Age Most stallions enter stud when they're 3 years or older, Squires said, and reach sexual maturity by the time they're 5 or 6. At some point, the stal- lion's testis begin to degenerate. But, like aging in general for horses, the point at which this occurs depends on the individual horse. "The timing for testicular degen- eration varies in stallions and may occur as early as 12 to 15 years or, in some stallions, after 20 years of age," Squires said. But the bottom line is that, in general, stallions' semen output will decrease as he ages. Thus, it's impor- tant to re-evaluate a stud's book each year to ensure he's not being stretched too thin. Season At many Kentucky Thor- oughbred farms, the breeding sheds open in mid- to late-February. At farms in more northern locations, the breeding season might not start until late spring or even early sum- mer. But while stallions are expected to impregnate mares at multiple times during the year, the season can have a signifi cant impact on how much sperm they produce. "Sperm output in the winter is about half of what it is in late spring and summer," Squires explained. "This seasonality is controlled by the length of daylight." He said breeders can increase stal- lions' sperm counts in February and March by keeping them under artifi - cial light for longer periods, starting in mid-December. However, he explained that managers generally do not place stallions under lights because, even though the sperm output will increase earlier in the year, sperm numbers will also decline earlier. This could pose a problem for late-season breeding. He warned breeders against overbook- ing stallions for the early parts of the breeding season, as decreased sperm output could be a concern. Testis size Size matters when it comes to a stallion's testis, and veteri- narians can garner important informa- tion by evaluating these structures. "Testicular volume can be used to determine whether the stallion has B luegrass Equine DIGEST CA.UKY.EDU/EQUINE ❙ THEHORSE.COM ❙ NOVEMBER 2015 In T is Issue Manifestations of Equine Herpesvirus-1 02 The Grass Guide: Kentucky Bluegrass 03 Grad Student Spotlight 04 ISTOCK.COM What Impacts Stallions' Sperm Output? Stallion sperm output in the winter is about half of what it is in late spring and summer. E - NEWSLETTERS Get Horse Health News Delivered To You! The Right Nutrition Equine Enteric Coronavirus CURRENTLY on Independent nutritionist Clair Thunes, PhD, offers research-backed equine nutrition advice each week, only on TheHorse.com! Submit your questions to THEditorialStaff@TheHorse.com. Sponsored by Purina. ■ Nutrition News Year's Resolutions TheHorse.com/36922 ■ Sugars and Peppermints: Not Safe Treats for All Horses TheHorse.com/36904 ■ Feeding the OTTB-Turned-Barrel-Horse TheHorse.com/36842 Sacrifice Areas on Horse Farms In this short video, learn how using drylots in your horse management can help you maintain healthy pastures. TheHorse.com/36851. Emerging virus or incidental bystander? Nicola Pusterla, DVM, PhD, Dipl. ACVIM, of the Uni- versity of California, Davis, shares insight into this infectious disease with an hourlong video presentation. TheHorse.com/36917. Become an Organized Horse Owner in 10 Days Mud Management and Horses Learn about the health risks mud poses to horses and how to get it under control on your property. Horses for Clean Water's Alayne Blickle and a veterinarian TBA will help field your questions during this live event! Visit TheHorse.com/AskTheHorseLive . Thursday, Jan. 21, 2016, at 8 p.m. EST Equine behavior consultant and researcher Rob- in Foster, PhD, CAAB, IAABC, helps you better understand your horses. Submit your questions to THEditorialStaff@TheHorse.com. ■ Stop the Mugging! Using Treats in Equine Training TheHorse.com/36895 ■ Is There Really Such Thing as a "Woman's Horse"? TheHorse.com/36731 Your Equine Behavior Questions Answered PHOTOS.COM ANNE M. EBERHARDT/THE HORSE ERICA LARSON Winter Wear for Horse People Keep warm around the barn, even during the coldest months, with tips from this slideshow: TheHorse.com/36936.